As a starter, a quick google identified a certain Curry Mulholland who played for Crusaders in the 50’s. As you are probably aware, Crusaders are based in Belfast. Probably 2+2 making 5 and like you I think it will need one of our Irish friends to confirm.

According to Football League Players Records 1946 - 92 the only Belfast born Mulholland who played professionally is Frank.All the others are Scots ,, George born Ayr 1928,, James born , Glasgow1938,, John. A , born Dumbarton 1932,, John R , born Dumbarton 1932 Perhaps the player in your photo never played as a pro Pete?

It could still be Curry Mulholland of Crusaders though but nobody has yet found a photo of him. Seeing as he's their record goalscorer (until recently) there must surely be some sort of evidence of him somewhere.